Family background

Maghnus was a son of King Tairrdelbach Ua Conchobair (1088-1156) and one of his six wives.

Crich Coirpre

Magnhus and his brother, Brian Luighnech Ua Conchobhair, were killed at the battle of Crich Coirpre in County Sligo by King Flaithbertaigh of Tyrconnell. The battle occurred on the Saturday before Whitsun

Whitsun

Whitsun is the name used in the UK for the Christian festival of Pentecost, the seventh Sunday after Easter, which commemorates the descent of the Holy Spirit upon Christ's disciples...

tide, Sixteen of the sons of the lords and chieftains of Connacht were slain by the Kinel Connell, as well as many others, both of the nobles and the plebians.

As a result of this battle, They (they Cenel Conaill

Cenél Conaill

The Cenél Conaill is the name of the "kindred" or descendants of Conall Gulban, son of Niall Noígiallach defined by oral and recorded history. They were also known in Scotland as the Kindred of Saint Columba....

) held the Connacians under subjection for a long time. Among the notable dead were two sons of Aed Ua Conchobair, Aed mac Conchobair Ua Cellaigh, Gilla Crist Ua Roduibh, Eachmarchach Ua Murray, a son of Mortough Ua Conchobair, three of the O'Mulrenins; the two Mac Gillaboys; and Hugh, son of Hugh, who was the son of Roderic, together with many others of the nobility

Nobility

Nobility is a social class which possesses more acknowledged privileges or eminence than members of most other classes in a society, membership therein typically being hereditary. The privileges associated with nobility may constitute substantial advantages over or relative to non-nobles, or may be...

.

Brian Luighneach's son, Donogh, was also killed.

Children and descendants

Maghnus's descendants were known as the Clann Maghnusa (LNG, pp. 398–99), which Jaski identifies as Mac Magnusa of Tir Tuathail (EIKS, p. 316). This would place them in County Roscommon

County Roscommon

County Roscommon is a county in Ireland. It is located in the West Region and is also part of the province of Connacht. It is named after the town of Roscommon. Roscommon County Council is the local authority for the county...

.

Magnus had the following known offspring:

• Muircheartach - alive 1230
• Diarmaid - His son Manus was killed in 1237. Another son, son Conchobair, was killed in 1279
• Domnall - A great-grandson, Teige, a man distinguished for his hospitality, was slain [in 1307) by Cathal, the son of Donnell, son of Teige O'Conor.
• Riocaird - In Leabhar na nGenealach
  Leabhar na nGenealach
  Leabhar na nGenealach is a massive genealogical collection written mainly in the years 1649 to 1650, at the college-house of St. Nicholas's church, Galway, by Dubhaltach MacFhirbhisigh. He continued to add material until at least 1666, five years before he was murdered in 1671...
  
  , Dubhaltach MacFhirbhisigh states that a clann Riocaird is from Riocard s. Maghnus s. Toirdhealbhach Mor; from him it was first named, i.e., it was called Clann Riocaird, for it was by (?) and from that Clann Riocard that Meic Cathail Leithdheirg came. Riocaird does not appear in the annals.